zk60镁合金的组织与腐蚀性能研究

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1、摘要摘要本文采用光学显微镜、扫描电镜、能谱分析和X射线衍射分析，以及静态失重法、电化学测试和力学性能测试等手段，系统研究了铸态ZK60合金不同热处理状态的组织与腐蚀性能，以及变形ZK60合金不同热处理状态的腐蚀性能与力学性能，并进一步探讨了稀土Nd对ZK60合金组织和腐蚀性能的影响。实验结果表明：铸态ZK60合金由α-Mg固溶体和晶界的MgZn相和MgZn2相组成，铸态合金因第二相偏析严重且晶界不连续分布，耐蚀性较差。时效使大量的第二相沿晶界析出，晶粒更为细小，其连续网状晶界可以有效提高耐腐蚀性能；均匀化处理使Mg

2、Zn相固溶入基体，且晶界断续，其耐蚀性最差；固溶加人工时效合金的晶界大多为颗粒状或短杆状，不能阻挡腐蚀进行，耐蚀性较差。轧制时效合金比轧制退火合金晶界析出物多，增多了微电偶腐蚀数目，降低了其腐蚀性能。商用变形ZK60合金存在择优取向。时效和固溶加人工时效后腐蚀速率与原始退火合金差别不大，同一温度时效时间越长，耐腐蚀性能越差。人工时效使合金的屈服强度大幅度提高，固溶加人工时效处理使合金的抗拉强度和屈服强度都有所下降。ZK60-1%Nd合金由α-Mg基体和晶界的MgZn相、MgZn2相和Mg12Nd相组成。加Nd后晶粒

3、更为细小，晶界结构连续和紧实，晶界宽而明显，大量带状或链状组织相互连接成网状，Nd的加入大大提高了ZK60合金的耐腐蚀性能。关键词：ZK60镁合金，腐蚀，热处理，微观组织IABSTRACTABSTRACTInthispaper,themicrostructureandcorrosionresistanceofas-castZK60alloyindifferentheattreatmentstates,andtheeffectofheattreatmentoncorrosionresistanceandmechani

4、calpropertiesofrolledZK60alloywerestudied.Theinfluenceofrareearth-NdonmicrostructureandcorrosionresistanceofZK60alloywerealsoinvestigatedsystematicallybyOM,SEM,EDS,XRD,testsofstaticweight-loss,aswellastestsofpolarizationcurvesandmechanicalpropertiesrespectivel

5、y.Theresultsindicatedthatas-castZK60alloywascomposedofα–Mgsolidsolution,MgZnandMgZn2phases.Thisalloyshowspoorcorrosionresistanceforitsserioussegregationanddiscontinuousboundary.Agingtreatmentproducedalargenumberofprecipitatesalonggrainboundaries,whichmadethegr

6、ainssmaller.Suchacontinuousgrainboundarymeshcaneffectivelyimprovecorrosionresistance.Homogenizationmadepartofthesecondphaseintosolidmatrix,itscorrosionresistancewasworstfordiscontinuousgrainboundaries.Experiencedwithsolutionandartificialagingtreatment,thealloy

7、hadverybadcorrosionresistanceduetobrokenorshortrodinggrainboundarieswhichcannotblockcorrosion.Agedrollingalloyhadmoreprecipitatesalonggrainboundariesthanannealedrollingalloysoincreasedthenumberofmicro-galvaniccorrosionsites,thusreduceditscorrosionresistance.Co

8、mmercialdeformedalloyexistedacertainorientation.Thecorrosionratesofagedalloyandsolutionandartificialagedalloyhadlittledifferencecomparedwiththeoriginalannealedalloy.Butatthesameagi